Resin bottles, representatives of which are oriented polypolypropylene (OPP) bottles and polyethylene terephthalate (PET) bottles, are used in various fields, such as beverages, foods, cosmetics, and so forth. Such a bottle is typically formed in a predetermined shape by biaxially stretch blow molding a resin preform by using a blow molding device in a state where the resin preform is heated to a temperature at which a stretching effect may be achieved. The resin preform has been formed in a bottomed tubular shape by, for example, injection molding.
Known examples of such a blow molding device include the one that uses a pressurized liquid, instead of pressurized air, as the pressurized fluid that is supplied into the preform. As the liquid to be pressurized in this example, a content liquid, such as a beverage, a cosmetic product, and a pharmaceutical product, that is to be filled into the bottle as a final product may be used. By doing so, the process of filling the content liquid to the bottle may be omitted, and the production process and the configuration of the blow molding device may be simplified.
For example, JP 2013208834A describes a blow molding device including a blow molding mold to which a preform, after heated to a temperature at which the preform is stretchable, is fitted, a blow nozzle that is fitted to a tubular mouth portion of the preform fitted to the mold, a pressurized liquid supply unit configured to supply a pressurized liquid into the preform through the blow nozzle, and a stretching rod that is freely displaceable in upward and downward directions. By stretching the preform in the longitudinal (axial) direction with the stretching rod and also by stretching the preform in the lateral (radial) direction by supplying the pressurized liquid into the preform, the preform is molded into a bottle having a shape conforming to a cavity of the mold.
Furthermore, to prevent the tubular mouth portion of the preform from undergoing diameter increase and deformation due to the pressure of the liquid supplied into the preform and causing the liquid to leak to the outside from a gap defined between the tubular mouth portion and the blow nozzle, the blow molding device described in JP 2013208834A also supplies air pressurized by a cylinder or the like to air space defined for pressurizing an outside of a mouth and surrounding an outer circumference of the tubular mouth portion of the preform fitted to the mold. The supplied pressurized air presses the tubular mouth portion against an outer circumferential surface of the blow nozzle and prevents the diameter increase and deformation of the tubular mouth portion.